In the drilling of wells, drilling fluid or mud is ordinarily circulated through the drill string and well bore. Such mud is pumped into the kelly at the upper end of the drill string and passes through the kelly into the drill string suspended therefrom. It is periodically necessary to disconnect the kelly from the remainder of the drill string, for example, in order to add additional sections of pipe to the string or to remove pipe sections therefrom. At such times, the mud pumps are shut down so that mud will not continue to be pumped through the kelly while it is disconnected. However, a significant quantity of mud remains in the kelly downstream of the pump, and can thus spill from the lower end of the kelly onto the rig floor when the kelly is disconnected.
Such spillage has a number of disadvantages, not the least of which is waste of the mud itself. The wasted mud spills onto the floor of the drill rig making the work site messy and unpleasant. Furthermore, the mud is usually slippery, and its presence on the equipment and the rig floor make the work difficult and even hazardous for the crew. Additionally, it is impossible for the crew to work on or with the kelly while the mud is flowing therefrom, and they must, therefore, wait for the mud to drain before continuing with their work. This in turn increases the time and expense of any given operation.
In an effort to aleviate the above described problems, various valve devices have been designed for disposition at the lower end of the kelly to prevent spilling of the mud therefrom when the kelly is disconnected from the drill or operating string. One such effort is represented by the kelly valve as shown and described in my copending application Ser. No. 881,188, filed Feb. 27, 1978, now abandoned. Field experience with that kelly valve revealed a number of deficiencies. One such deficiency was that the inner valve body, which was a cylinder of elastomeric material with flanged end portions, had to be deformed in order to assemble it onto the outer valve body, and such deformation caused weakness which lead to early failure. Another deficiency was that, when subjected to mud flow pressures, the inner valve body would take a permanent set at its end regions where it was secured to inwardly extending flange portions of the outer valve body, thus producing further weakness contributing to early failure. Another deficiency was the complexity of assembly and disassembly due to securing of the inner body member to the outer body member by means of bolt rings. A further deficiency was that the maximum inner diameter of the kelly valve was limited due to the inwardly extending flange portions of the outer valve body.
It is accordingly the general object of this invention to provide an improved kelly valve.
Another object of the invention is to provide a kelly valve which obviates the deficiencies of the kelly valve disclosed in said co-pending application.
For a further understanding of the invention and further objectives, features, and advantages thereof, reference may now be had to the following description, taken in conjunction with the accompanying drawings.